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What will cause a hesitation in a 3.9L engine when driving at 55-70mph while accelerating?
Wiki User
∙ 12y ago
Lots of possibilities or combinations of things. Start with checking for a dirty air filter or a restriction in the air intake system. Check all vacuum lines for vacuum leaks. Check spark plugs for cleanliness and proper gap, check the spark plug wires for any signs of damage or leaks (yes, they can leak, causing the electrical energy to arc out of the wire before it gets to the plug). If the plugs and wires, distributor cap and rotor (if equipped; no model year was mentioned here) have not been replaced within the last few years, it would be prudent to replace them now. Essentially, give the engine a tune-up.
Failed oxygen sensors or a bad catalytic converter may be a factor as well.
Other possibilities could be fuel related. Dirty, water-contaminated, or poor-quality fuel can cause hesitation, or poor starting. A fuel additive to remove water and clean your fuel system might be worth trying. Try to use good quality fuel from reputable sources. I'm not saying use higher octane, that's a waste of money and contrary to manufacturer's recommendations for newer engines, I'm saying cheap fuel is usually cheap for a reason (trust me, I truck it from time to time). Spend the extra pennies per liter for better fuel, it's cheaper, long term.
Lastly, the fuel system itself could be At Fault. The fuel filter could be plugged, the fuel lines could be restricted or leaking, the fuel pump could be faulty. Fuel injectors could be worn out or dirty.
Wiki User
∙ 12y ago
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